1. Field of the Invention
This invention relates to lightweight, portable, vibrating concrete screeds and more specifically to screeds of this type having a winching mechanism.
2. Description of the Prior Art
A lightweight, portable, vibrating concrete screed of a type to which the present invention is applicable is fully described in applicant's prior U.S. Pat. No. 4,030,873. The general state of the art with respect to the type of screeds to which the present invention relates is believed to be fully set forth in such patent and therefore will not be repeated. Reference is also made to applicant's copending application, Ser. No. 883,955 filed Mar. 6, 1978 entitled "Portable Vibrating Concrete Screed" in which there is shown a winching means driven by a gasoline engine on the screed such that the screed may be winched automatically, at varying angles and at different speeds at each end of the screed. However, the winching mechanism referred to in such copending application does not provide a detachable winching unit driven by the shaft through a fluid motor and with all of the advantages of the winching unit of the present invention as later described.
Another type of self-propelled screed having a winch mechanism is manufactured by the Racine Construction Tool Company, 2200 South Broad Street, Racine, Wis. 53404. Unlike the detachable winching unit of the present invention, the winch mechanism of this reference does not utilize a vibrating screed shaft as the drive mechanism for the winching unit. Further, the winching mechanism described in this reference does not provide a detachable winching unit which can be mounted at each end of a screed frame or at each end of a plurality of interconnected screed frames.
Other types of winching mechanisms for screeds are found in U.S. Pat. Nos. 3,412,658 and 4,132,492.
With the foregoing prior art and all other prior art in mind of which applicant has knowledge, it seems evident that the prior art has not provided a lightweight, portable, vibrating concrete screed of the open frame and vibrating shaft type as described in U.S. Pat. No. 4,030,873 with a detachable winching mechanism that can be driven from the vibrating shaft and that can be quickly adapted to any length of screed made up of interconnected screeding units. From a practical viewpoint, the prior art has not provided such a detachable winching mechanism which itself is designed as a unitary screeding unit for imparting uniform vibrations throughout its length to complement the uniform vibrations imparted throughout the length of the screeding unit to which the screeding mechanism unit is attached.